Manufacture of artificial materials



Patented Aug. 6, 19 40 UNITED" STATES MAnor'Aorvnn oF ARTIFIQIALMATERI S Henry Dreyfus, London," England Application Jane 18, 1937,.seria1 No. 148,969. In Great Britain Julyl, 193,6

6 Claims. (01. 188) This invention relatesto improvements in the manufacture of artificial materials, and particularly to improvements ,in the manufacture of filaments, yarns and similar materials, especially such materials having a basis of cellulose acetate or other organic derivative [of cellulose, by wet spinning processes. H i 1 When artificial filamentsand other products are manufactured by extruding, solutions into liquid coagulatingmedia the drag on the materials due to their motionthrough the liquid may be considerable, and. it of course increases'very rapidly as their velocity increases-.3 It has been discovered that this drag mayhave a deleterious effect upon the properties of the artificial products, particularly upon their tenacity and extensibility, and thatimproved products may be obtained by carrying out thespinningoperation sothat the drag is reduced or eliminated.

The relative velocity of the materials, with respect to the coagulating medium may be reduced by circulating the coagulating medium so that it travels in the samedirection as thematerials, but it has been found that unless precautions are taken turbulent motion may be set up in the coagulating, medium and this turbulent motion may cause difficulties in spinning-and may also be detrimental to the properties of, the DIOd-r ucts obtained. According to the present invention artificial filaments and other materials are produced, particularly at high spinning speeds, for example spinning speeds of 01' 200to 300 metres per minute or even 400 metres per minute-or more, by wet spinning processesin which the coagulatingmedia move with a substantially streamline flow in the direction of travel of the materials. The invention is also concerned with apparatus whereby this streamline ,fiow. may be achieved.

Turbulence in thecoagulating medium may be reduced or eliminated by means of sheets 01' gauze or similar finefmesh material extending across the coagulating vessel. One or more of such sheets, for example 2, 3 or more, may be inserted behind the jet and others at the end of, the coagulating vessel after the point at which the artificial materials emerge. The presence of such sheets assists in breaking up any turbulence due, forv example, to the flow of liquid. Pulsation due to the pump or other circulating device may be reduced by having a vesselof large capacity in relation tothe rate of flow of liquid in between the circulating device and the'jet, e. g., a capacity such that the liquid circulated requires .atleast 30 secs. or 1 minute to pass through it. Preferably it has a large cross-sectional area so that the linear velocity of the liquid through it is low, e. g., 3-4 yards/minute. It may containsheets of fine mesh material extending across it to assist in dampingout pulsation or turbulence, and/or bailles to prevent the liquorfrom taking a direct path from the inlet totheoutlet. v

The shape of the jet employed may also have a considerable efiect on the nature of the liquid flow, and by; suitably designing the jet turbulence maybe reduced. For example, an improved flow may be obtained by using, instead of the usual type of jet, a; jet "having streamline contours. Thusa line jet may be employed having a cross- 1'6 section of streamline contours in the direction. of fiow,-the orifices through which the solution is extrudedbeing formed in the end of thetapered portion. Preferably thev lateral extremities of the jet are also streamlined. Another Iorm'cf jet so which may beemployedis one having the shape of the solid formed by the revolution of the cross-section described above about .its longitudinal axis. In this case the jet orifices may be formed in .a plane normal to the longitudinal :5 axis and passing through the tapered portion, and their axes should be substantially parallel to the longitudinal axis of the jet.

.When artificial filaments or other materials are stretched in the coagulating bath their veloc- 30 ity increases along the length of the bath, and in order to increase the velocity of the coagulating' medium at the same rate the cross-section of the bathmay diminish at the necessary rate in' the direction of travel of the materials.

.The invention is particularly concerned with wet spinning processes in which the. coagulating medium flows at substantially the same rate as the rate of travelof the artificial materials, though, if desired, there may be a difference in 4 the velocities of the materials and the coagulating liquid. For example, the coagulating liquid may flow at a higher speed than the materials so that it exerts adrag upon them which assists in stretching them, providedthat thedrag is not 45' so great that the properties of the materials are detrimentally affected. Processes of thischaracter are described in U. S. Patent No. 2,027,419, which describes the use of coagulating media of high vviscosities so that they are capable of exert- 60' ing-considerable drag. The present invention, however, is particularlyconcerned with avoiding any drag on the materials-due to the coagulating medium, and therefore, jin general, no additions aramade to tbe c su atinamediafor the. pur- 6.5

pose of increasing their viscosities. Thus the coagulating media employed may have a viscosity less than, or at least not substantially greater than, that of water.

The coagulating vessels employed according to the present invention may be arranged so that the artificial materials travel in a substantially horizontal direction, or they may be vertical in which case the materials may be extruded either upwards or downwards.

A further method of reducing the drag on the artificial materials comprises spinning under such conditions that the materials are sufficiently set after only a relatively short run through the coagulatingmedium, for example a run of only 6 inches or 4 inches or even less. For example, instead of using an aqueous coagulating bath containing 60% of diacetone alcohol as is described in Example 1 of British Patent No. 340,324 and immersing the filaments in the bath for a length of 8 to 10 inches, an aqueous bath containing only 50% or 40% of diacetone alcohol may be employed and the length of immersion may thus be reduced to 6 inches or 4 inches or less. The composition of the bath and the length of immersion necessary to obtain the desired degree of coagulation will depend upon the rate of spinning and, in general, as the rate of spinning increases the coagulating power of the coagulating medium should be increased for any given length of immersion. Thus when aqueous coagulating media containing substantial proportions of relatively non-volatile solvents, such as are described in British Patent No. 340,324 are employed, the proportion of solvent may be decreased with increasing rates of spinning. For example if for a given length of immersion a coagulating medium containing 50% of diacetone alcohol or glycol monoacetate is satisfactory at a spinning speed of metres per minute, when the spinning speed is increased, for example to 200 metres per minute, the concentration may be decreased to 45 or 40% or even less according to the degree of coagulation and the draw down required.

Preferably spinning solutions comprising cellulose acetate or other organic derivative of cellulose dissolved in relatively volatile solvents, e. g. acetone, methylene ethylene ether or dioxane, are employedaccording to the process of the present invention and such solutions may contain higher boiling solvents, for example glycol mono-acetate, methyl glycol mono-acetate, diacetone alcohol and ethyl lactate. Coagulating media containing substantial proportions of relatively non-volatile solvents, such as those mentioned above and described in British Patent No. 340,324, are particularly suitable, though other coagulating media, for example solutions of salts, may be employed.

Examples of apparatus according to the present invention are illustrated diagrammatically in the accompanying drawing, wherein Figures 1 and 2 show respectively a sectional elevation and a plan view of a coagulating vessel containing sheets of gauze;

Figures 3'-'and 4 show a cross-section and an end view of a streamline jet in which the orifices are arranged in a circle;

Figure 5 shows an end view of a streamline jet in which the orifices are arranged in two lines, and Figure 6 a cross-section'of the jet on the line 6ii of Figure 5, the cross-section on the line 3-3 being similar to that shown in Figure 3; and

Figure 7 shows a wet spinning apparatus which comprises a vessel of large capacity to assist in reducing turbulence.

The apparatus illustrated in Figures 1 and. 2 comprises a coagulating vessel I0 containing a streamline jet I I provided with a candle filter l2. The vessel comprises inlet and outlet connections I3 and I4 for the coagulating medium. In front of the orifice I3 is positioned a gauze l5, and gauzes I6 are fitted just behind the jet H and in the outlet M.

The jet illustrated in Figures 3 and 4 comprises a hollow body portion 2| having an inlet 22 for spinning solution and provided with spinning orifices 23, the axes of these orifices being substantially parallel to the longitudinal axis of the jet.

The jet illustrated in Figures 5 and 6 has a cross-section on the line 33 similar to that shownin Figure 3 and comprises two rows of orifices 23, the axes of which are substantially parallel to the plane of symmetry passing between the two lines of orifices. The ends of the jet are streamlined as indicated by the cross-section shown in Figure 6 taken on the line 66 of Figure 5.

The apparatus illustrated in Figure 7 comprises a coagulating vessel l0 containing a streamline jet l I of the type illustrated in Figures 3 and 4 which is provided with a candle filter l2 and inlet and outlet pipes l3 and M for the coagulating medium. It also comprises gauzes I5 and Hi. The outlet pipe I4 is connected with a pump 24 for circulating the coagulating medium, the outlet side of the pump being connected by a pipe 21 with a vessel 25 of large capacity from which the coagulating medium passes into the coagulating vessel through the pipe I3. The inlet pipe 21 is carried to near the top of the vessel which contains a partition 28 extending nearly to the bottom and two horizontal gauzes 29 and 3G. The coagulating medium introduced into the vessel is thus forced to flow down one side of the partition and then up the other slde through the gauzes before reaching the outlet pipe I3. The vessel 25 is provided with an outlet 26 for removing the coagulating medium if required.

The present invention is particularly concerned with the manufacture of artificial filaments and similar materials having a basis of cellulose acetate and other organic derivatives of cellulose, for example cellulose formate, cellulose propionate, cellulose butyrate, cellulose nitro-acetate and other cellulose esters and mixed esters, methyl, ethyl, propyl and butyl celluloses, and other cellulose ethers and mixed ethers, and mixed etheresters, for example ethyl cellulose acetate and oxy-ethyl cellulose acetate.

Having described my invention what I desire to secure by Letters Patent is:

1. Apparatus for the production of artificial filaments, yarns and similar materials by wet spinning processes, which comprises a vessel for coagulating medium provided with an inlet and an outlet for said medium and with fine mesh material extending across the vessel and substantially normal to the direction of flow of the medium.

2. Apparatus for the production of artificial filaments, yarns and similar materials by wet spinning processes, which comprises a vessel for coagulating medium provided with an inlet and an outlet for said medium and with sheets of gauze extending across the vessel and substantially normal to the direction of flow of the medium.

3. Apparatus for the production of artificial filaments, yarns and similar materials by wet spinning processes, which comprises a vessel for coagulating medium provided with an inlet and an outlet for said medium, With fine mesh material extending across the vessel substantially normal to the direction of flow of the medium,

I and with a spinning jet having streamlined contours and positioned in said vessel downstream of the fine mesh material.

4. Apparatus for the production of artificial filaments, yarns and similar materials by wet spinning processes, which comprises a vessel for coagulating medium provided with an inlet and an outlet for said medium, with sheets of gauze extending across the vessel substantially normal to the direction of flow of the medium, and with a spinning jet having streamlined contours and positioned in said vesseldownstream of the sheets of gauze. I

5. Process for the production of artificial filaments, yarns and similar materials, which comprises extruding a solution of a filament-forming base through a shaping orifice directly into a bath of coagulating liquid moving in substantially the same direction as the extruded materials and in a manner such that all the extruded materials are immediately contacted by the coagulating liquid of the bath, and while the coagulating liquid is moving in the direction of the extruded materials subdividing said coagulating liquid, at a point prior to the point of contact of the same with the extruded materials, into a large number of parallel streams and allowing the streams to reunite so as to produce a substantial stream-line flow of the coagulating liquid in the direction of movement of said extruded materials.

6. Process for the production of artificial filaments, yarns and similar materials, which comprises extruding a solution of a filament-forming base through a shaping orifice directly into a bath of coagulating liquid moving in the same direction and at substantially the same velocity as the extruded materials and in a manner such that all the extruded materials are immediately contacted by the coagulating liquid of the bath, 

